I'm in a large school compared to yours (classes)...but high staff turnovers can still happen for entirely innocent reasons. One year over half of our teaching staff was new as one member of staff sadly died suddenly, another left due to ill health and 3 teachers chose to retire at the same time. I later heard that some people had been put off applying for posts at my school by this as they assumed it was a reflection of something strange.
Yes it can have an impact as the teachers won't know the kids or the school setup, but sometimes it can be good as new staff can bring innovation and new ideas.
Heads and deputies are paid according to the number on role (a friend of mine is the head of a small school and she earns less than her partner who is deputy of a large primary), so some small schools do experience a high turnover of headteachers as a deputy will attain a headship in a small school, then use this experience to attain a headship in a larger school.
Whilst I agree with the above, I would be concerned especially with the fact they are just meant to disappear! Why don't you write to the Chair of Governors and ask? You should be able to tell from his/her reply whether it is coincidence or an unhappy school.
80 pupils would mean 3 or at the most 4 classes so that many teachers too. 2 teachers leaving wouldn't even cause a blink in most large schools, the impact is obviously greater in a small school but might not have any underlying reason, promotion opportunities are limited in small schools so turnover can be higher ( although I've been at my small school for nearly 8 years!)
My school is 3 form entry and we are losing 9 teachers + about 10 support staff. No sinister reasons at all, all are due to moving away from the area/ maternity leave/ retirement and starting teacher training, but anyone looking from the outside at just the numbers would probably be hugely concerned! If it is a small school then coincidences can mean the majority leaving, however if they are having a problem retaining a head then this could be a cause. Hopefull they will now have the right person in post which mean staff turnover should settle down.
If its a very small school and the staff are close-knit and worked together for years it doesn't surprise me if many leave together. I've seen this happen when a head retires and many of the other staff decide they would rather retire or persue other work, like supply or tutoring, than work with a new head who will want to make sweeping changes (new broom, etc.) If it is their third head, maybe the staff are just fed up with a new head coming in, making changes, then moving on? If there are only about 80 pupils there can't be many teachers, so a few leaving is a huge percentage.
5 classes with 80 children = hard to manage the books (funding basically assumes 30 children per teacher, a long way less than this and budgets get tight) and this may contribute to the high turnover of heads..... and perhaps to a high number of newly qualified teachers being taken on as they are cheaper (but conversely more mobile)...